NON-WORKING: can't spawn a thread because the closure would outlive reports.

Batch up TxReports for entire transaction.
Notify observers about committed transaction.
Store transaction observer service inside Conn

db/Cargo.toml

@@ -5,6 +5,7 @@ workspace = ".."
 
 [dependencies]
 error-chain = { git = "https://github.com/rnewman/error-chain", branch = "rnewman/sync" }
+indexmap = "0.4"
 itertools = "0.7"
 lazy_static = "0.2"
 num = "0.1"

db/src/lib.rs

@@ -13,6 +13,7 @@
 
 #[macro_use]
 extern crate error_chain;
+extern crate indexmap;
 extern crate itertools;
 
 #[macro_use]
@@ -45,6 +46,7 @@ pub mod errors;
 pub mod internal_types;    // pub because we need them for building entities programmatically.
 mod metadata;
 mod schema;
+pub mod tx_observer;
 mod watcher;
 mod tx;
 pub mod types;
@@ -85,7 +87,13 @@ pub use tx::{
     transact_terms,
 };
 
+pub use tx_observer::{
+    TxObservationService,
+    TxObserver,
+};
+
 pub use types::{
+    AttributeSet,
     DB,
     PartitionMap,
     TxReport,

db/src/tx.rs

@@ -51,8 +51,9 @@ use std::collections::{
     BTreeSet,
     VecDeque,
 };
-
-use std::rc::Rc;
+use std::rc::{
+    Rc,
+};
 
 use db;
 use db::{
@@ -106,6 +107,7 @@ use schema::{
 };
 use types::{
     Attribute,
+    AttributeSet,
     AVPair,
     AVMap,
     Entid,
@@ -527,8 +529,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
     /// This approach is explained in https://github.com/mozilla/mentat/wiki/Transacting.
     // TODO: move this to the transactor layer.
     pub fn transact_entities<I>(&mut self, entities: I) -> Result<TxReport>
-    where I: IntoIterator<Item=Entity>,
-          W: TransactWatcher {
+    where I: IntoIterator<Item=Entity> {
         // Pipeline stage 1: entities -> terms with tempids and lookup refs.
         let (terms_with_temp_ids_and_lookup_refs, tempid_set, lookup_ref_set) = self.entities_into_terms_with_temp_ids_and_lookup_refs(entities)?;
 
@@ -542,8 +543,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
     }
 
     pub fn transact_simple_terms<I>(&mut self, terms: I, tempid_set: InternSet<TempId>) -> Result<TxReport>
-    where I: IntoIterator<Item=TermWithTempIds>,
-          W: TransactWatcher {
+    where I: IntoIterator<Item=TermWithTempIds> {
         // TODO: push these into an internal transaction report?
         let mut tempids: BTreeMap<TempId, KnownEntid> = BTreeMap::default();
 
@@ -614,7 +614,9 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                                                     final_populations.allocated,
                                                     inert_terms.into_iter().map(|term| term.unwrap()).collect()].concat();
 
+
         let tx_instant;
+        let mut affected_attrs = AttributeSet::new();
 
         { // TODO: Don't use this block to scope borrowing the schema; instead, extract a helper function.
 
@@ -669,6 +671,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
                     }
 
                     self.watcher.datom(op, e, a, &v);
+                    affected_attrs.insert(a);
 
                     let reduced = (e, a, attribute, v, added);
                     match (attribute.fulltext, attribute.multival) {
@@ -735,6 +738,7 @@ impl<'conn, 'a, W> Tx<'conn, 'a, W> where W: TransactWatcher {
             tx_id: self.tx_id,
             tx_instant,
             tempids: tempids,
+            changeset: affected_attrs,
         })
     }
 }

db/src/tx_observer.rs

@@ -0,0 +1,152 @@
+// Copyright 2018 Mozilla
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+// this file except in compliance with the License. You may obtain a copy of the
+// License at http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+use std::sync::{
+    Arc,
+    Weak,
+};
+use std::thread;
+
+use indexmap::{
+    IndexMap,
+};
+
+use types::{
+    AttributeSet,
+    TxReport,
+};
+
+pub struct TxObserver {
+    notify_fn: Arc<Box<Fn(&String, &Vec<&TxReport>) + Send + Sync>>,
+    attributes: AttributeSet,
+}
+
+impl TxObserver {
+    pub fn new<F>(attributes: AttributeSet, notify_fn: F) -> TxObserver where F: Fn(&String, &Vec<&TxReport>) + 'static + Send + Sync {
+        TxObserver {
+            notify_fn: Arc::new(Box::new(notify_fn)),
+            attributes,
+        }
+    }
+
+    pub fn applicable_reports<'r>(&self, reports: &'r Vec<TxReport>) -> Vec<&'r TxReport> {
+        let mut out = Vec::with_capacity(reports.len());
+        for report in reports {
+            if self.attributes.intersection(&report.changeset).next().is_none() {
+                continue;
+            }
+            out.push(report);
+        }
+        out
+    }
+
+    fn notify(&self, key: &String, reports: &Vec<&TxReport>) {
+        (*self.notify_fn)(key, reports);
+    }
+}
+
+pub trait Command {
+    fn execute(&mut self);
+}
+
+pub struct NotifyTxObserver<'r> {
+    key: String,
+    reports: Vec<&'r TxReport>,
+    observer: Weak<TxObserver>,
+}
+
+impl<'r> NotifyTxObserver<'r> {
+    pub fn new(key: String, reports: Vec<&'r TxReport>, observer: Weak<TxObserver>) -> Self {
+        NotifyTxObserver {
+            key,
+            reports,
+            observer,
+        }
+    }
+}
+
+impl<'r> Command for NotifyTxObserver<'r> {
+    fn execute(&mut self) {
+        self.observer.upgrade().map(|o| o.notify(&self.key, &self.reports));
+    }
+}
+
+pub struct AsyncBatchExecutor<'r> {
+    commands: Vec<Box<Command + Send + 'r>>,
+}
+
+impl<'r> Command for AsyncBatchExecutor<'r> {
+    fn execute(&mut self) {
+        // need to clone to move to a new thread.
+        let command_queue = ::std::mem::replace(&mut self.commands, Vec::new());
+        thread::spawn (move ||{
+            for mut command in command_queue.into_iter() {
+                command.execute();
+            }
+        });
+    }
+}
+
+pub struct TxObservationService {
+    observers: IndexMap<String, Arc<TxObserver>>,
+    pub command_queue: Vec<Box<Command + Send>>,
+}
+
+impl TxObservationService {
+    pub fn new() -> Self {
+        TxObservationService {
+            observers: IndexMap::new(),
+            command_queue: Vec::new(),
+        }
+    }
+
+    // For testing purposes.
+    pub fn is_registered(&self, key: &String) -> bool {
+        self.observers.contains_key(key)
+    }
+
+    pub fn register(&mut self, key: String, observer: Arc<TxObserver>) {
+        self.observers.insert(key, observer);
+    }
+
+    pub fn deregister(&mut self, key: &String) {
+        self.observers.remove(key);
+    }
+
+    pub fn has_observers(&self) -> bool {
+        !self.observers.is_empty()
+    }
+
+    fn command_from_reports<'r>(&self, key: &String, reports: &'r Vec<TxReport>, observer: &Arc<TxObserver>) -> Option<Box<Command + Send + 'r>> {
+        let applicable_reports: Vec<&'r TxReport> = observer.applicable_reports(reports);
+        if !applicable_reports.is_empty() {
+            Some(Box::new(NotifyTxObserver::new(key.clone(), applicable_reports, Arc::downgrade(observer))))
+        } else {
+            None
+        }
+    }
+
+    pub fn transaction_did_commit(&mut self, reports: Vec<TxReport>) {
+        let mut commands = Vec::with_capacity(self.observers.len());
+        for (key, observer) in self.observers.iter() {
+            if let Some(command) = self.command_from_reports(key, &reports, &observer) {
+                commands.push(command);
+            }
+        }
+        self.command_queue.push(Box::new(AsyncBatchExecutor { commands }));
+    }
+
+    pub fn run(&mut self) {
+        let command_queue = ::std::mem::replace(&mut self.command_queue, Vec::new());
+        for mut command in command_queue.into_iter() {
+            command.execute();
+        }
+    }
+}

db/src/types.rs

@@ -11,19 +11,22 @@
 #![allow(dead_code)]
 
 use std::collections::HashMap;
-use std::collections::BTreeMap;
+use std::collections::{
+    BTreeMap,
+    BTreeSet,
+};
 
 extern crate mentat_core;
 
 pub use self::mentat_core::{
-    DateTime,
-    Entid,
-    ValueType,
-    TypedValue,
     Attribute,
     AttributeBitFlags,
+    DateTime,
+    Entid,
     Schema,
+    TypedValue,
     Utc,
+    ValueType,
 };
 
 /// Represents one partition of the entid space.
@@ -82,6 +85,9 @@ pub type AVPair = (Entid, TypedValue);
 /// Used to resolve lookup-refs and upserts.
 pub type AVMap<'a> = HashMap<&'a AVPair, Entid>;
 
+// represents a set of entids that are correspond to attributes
+pub type AttributeSet = BTreeSet<Entid>;
+
 /// A transaction report summarizes an applied transaction.
 #[derive(Clone, Debug, Eq, Hash, Ord, PartialOrd, PartialEq)]
 pub struct TxReport {
@@ -97,4 +103,7 @@ pub struct TxReport {
     /// existing entid, or is allocated a new entid.  (It is possible for multiple distinct string
     /// literal tempids to all unify to a single freshly allocated entid.)
     pub tempids: BTreeMap<String, Entid>,
+
+    // A set of entids for attributes that were affected inside this transaction
+    pub changeset: AttributeSet,
 }

src/conn.rs

@@ -57,6 +57,8 @@ use mentat_db::{
     transact,
     transact_terms,
     PartitionMap,
+    TxObservationService,
+    TxObserver,
     TxReport,
 };
 
@@ -140,6 +142,7 @@ pub struct Conn {
 
     // TODO: maintain cache of query plans that could be shared across threads and invalidated when
     // the schema changes. #315.
+    tx_observer_service: Mutex<TxObservationService>,
 }
 
 /// A convenience wrapper around a single SQLite connection and a Conn. This is suitable
@@ -202,10 +205,10 @@ pub struct InProgress<'a, 'c> {
     generation: u64,
     partition_map: PartitionMap,
     schema: Schema,
-
     cache: InProgressSQLiteAttributeCache,
-
     use_caching: bool,
+    tx_reports: Vec<Arc<TxReport>>,
+    observer_service: Option<&'a Mutex<TxObservationService>>,
 }
 
 /// Represents an in-progress set of reads to the store. Just like `InProgress`,
@@ -374,6 +377,7 @@ impl<'a, 'c> InProgress<'a, 'c> {
                            self.cache.transact_watcher(),
                            terms,
                            tempid_set)?;
+        self.tx_reports.push(Arc::new(report.clone()));
         self.partition_map = next_partition_map;
         if let Some(schema) = next_schema {
             self.schema = schema;
@@ -397,6 +401,8 @@ impl<'a, 'c> InProgress<'a, 'c> {
                      &self.schema,
                      self.cache.transact_watcher(),
                      entities)?;
+        self.tx_reports.push(Arc::new(report.clone()));
+
         self.partition_map = next_partition_map;
         if let Some(schema) = next_schema {
             self.schema = schema;
@@ -440,6 +446,12 @@ impl<'a, 'c> InProgress<'a, 'c> {
         metadata.generation += 1;
         metadata.partition_map = self.partition_map;
 
+        // let the transaction observer know that there have been some transactions committed.
+        if let Some(ref observer_service) = self.observer_service {
+            let mut os = observer_service.lock().unwrap();
+            os.transaction_did_commit(self.tx_reports);
+        }
+
         // Update the conn's cache if we made any changes.
         self.cache.commit_to(&mut metadata.attribute_cache);
 
@@ -451,6 +463,12 @@ impl<'a, 'c> InProgress<'a, 'c> {
             // TODO: consider making vocabulary lookup lazy -- we won't need it much of the time.
         }
 
+        // run any commands that we've created along the way.
+        if let Some(ref observer_service) = self.observer_service {
+            let mut os = observer_service.lock().unwrap();
+            os.run();
+        }
+
         Ok(())
     }
 
@@ -564,9 +582,15 @@ impl Conn {
     fn new(partition_map: PartitionMap, schema: Schema) -> Conn {
         Conn {
             metadata: Mutex::new(Metadata::new(0, partition_map, Arc::new(schema), Default::default())),
+            tx_observer_service: Mutex::new(TxObservationService::new()),
         }
     }
 
+    #[cfg(test)]
+    pub fn is_registered_as_observer(&self, key: &String) -> bool {
+        self.tx_observer_service.lock().unwrap().is_registered(key)
+    }
+
     /// Prepare the provided SQLite handle for use as a Mentat store. Creates tables but
     /// _does not_ write the bootstrap schema. This constructor should only be used by
     /// consumers that expect to populate raw transaction data themselves.
@@ -705,6 +729,8 @@ impl Conn {
             schema: (*current_schema).clone(),
             cache: InProgressSQLiteAttributeCache::from_cache(cache_cow),
             use_caching: true,
+            tx_reports: Vec::new(),
+            observer_service: if self.tx_observer_service.lock().unwrap().has_observers() { Some(&self.tx_observer_service) } else { None },
         })
     }
 
@@ -786,6 +812,14 @@ impl Conn {
             },
         }
     }
+
+    pub fn register_observer(&mut self, key: String, observer: Arc<TxObserver>) {
+        self.tx_observer_service.lock().unwrap().register(key, observer);
+    }
+
+    pub fn unregister_observer(&mut self, key: &String) {
+        self.tx_observer_service.lock().unwrap().deregister(key);
+    }
 }
 
 #[cfg(test)]
@@ -798,19 +832,25 @@ mod tests {
     use std::collections::{
         BTreeSet,
     };
-
     use std::path::{
         PathBuf,
     };
-
-    use std::time::Instant;
+    use std::time::{
+        Duration,
+        Instant
+    };
+    use std::thread;
 
     use mentat_core::{
         CachedAttributes,
         TypedValue,
     };
 
-    use query::{
+    use ::entity_builder::{
+        BuildTerms,
+    };
+
+    use ::query::{
         PreparedQuery,
         Variable,
     };
@@ -821,6 +861,16 @@ mod tests {
         QueryResults,
     };
 
+    use ::vocabulary::{
+        AttributeBuilder,
+        Definition,
+        VersionedStore,
+    };
+
+    use ::vocabulary::attribute::{
+        Unique
+    };
+
     use mentat_db::USER0;
 
     #[test]
@@ -1381,4 +1431,219 @@ mod tests {
             assert_eq!(only_two, vec![1, 3].into_iter().map(TypedValue::Long).collect());
         }
     }
+
+    fn test_register_observer() {
+        let mut sqlite = db::new_connection("").unwrap();
+        let mut conn = Conn::connect(&mut sqlite).unwrap();
+
+        let key = "Test Observer".to_string();
+        let tx_observer = TxObserver::new(BTreeSet::new(), move |_obs_key, _batch| {});
+
+        conn.register_observer(key.clone(), Arc::new(tx_observer));
+        assert!(conn.is_registered_as_observer(&key));
+    }
+
+    #[test]
+    fn test_deregister_observer() {
+        let mut sqlite = db::new_connection("").unwrap();
+        let mut conn = Conn::connect(&mut sqlite).unwrap();
+
+        let key = "Test Observer".to_string();
+
+        let tx_observer = TxObserver::new(BTreeSet::new(), move |_obs_key, _batch| {});
+
+        conn.register_observer(key.clone(), Arc::new(tx_observer));
+        assert!(conn.is_registered_as_observer(&key));
+
+        conn.unregister_observer(&key);
+
+        assert!(!conn.is_registered_as_observer(&key));
+    }
+
+    fn add_schema(conn: &mut Conn, mut sqlite: &mut rusqlite::Connection) {
+        // transact some schema
+        let mut in_progress = conn.begin_transaction(&mut sqlite).expect("expected in progress");
+        in_progress.ensure_vocabulary(&Definition {
+            name: kw!(:todo/items),
+            version: 1,
+            attributes: vec![
+                (kw!(:todo/uuid),
+                AttributeBuilder::new()
+                    .value_type(ValueType::Uuid)
+                    .multival(false)
+                    .unique(Unique::Value)
+                    .index(true)
+                    .build()),
+                (kw!(:todo/name),
+                AttributeBuilder::new()
+                    .value_type(ValueType::String)
+                    .multival(false)
+                    .fulltext(true)
+                    .build()),
+                (kw!(:todo/completion_date),
+                AttributeBuilder::new()
+                    .value_type(ValueType::Instant)
+                    .multival(false)
+                    .build()),
+                (kw!(:label/name),
+                AttributeBuilder::new()
+                    .value_type(ValueType::String)
+                    .multival(false)
+                    .unique(Unique::Value)
+                    .fulltext(true)
+                    .index(true)
+                    .build()),
+                (kw!(:label/color),
+                AttributeBuilder::new()
+                    .value_type(ValueType::String)
+                    .multival(false)
+                    .build()),
+            ],
+        }).expect("expected vocubulary");
+        in_progress.commit().expect("Expected vocabulary committed");
+    }
+
+    #[derive(Default)]
+    struct ObserverOutput {
+        txids: Vec<i64>,
+        changes: Vec<BTreeSet<i64>>,
+        called_key: Option<String>,
+    }
+
+    #[test]
+    fn test_observer_notified_on_registered_change() {
+        let mut sqlite = db::new_connection("").unwrap();
+        let mut conn = Conn::connect(&mut sqlite).unwrap();
+        add_schema(&mut conn, &mut sqlite);
+
+        let name_entid: Entid = conn.current_schema().get_entid(&kw!(:todo/name)).expect("entid to exist for name").into();
+        let date_entid: Entid = conn.current_schema().get_entid(&kw!(:todo/completion_date)).expect("entid to exist for completion_date").into();
+        let mut registered_attrs = BTreeSet::new();
+        registered_attrs.insert(name_entid.clone());
+        registered_attrs.insert(date_entid.clone());
+
+        let key = "Test Observing".to_string();
+
+        let output = Arc::new(Mutex::new(ObserverOutput::default()));
+
+        let mut_output = Arc::downgrade(&output);
+        let tx_observer = Arc::new(TxObserver::new(registered_attrs, move |obs_key, batch| {
+            if let Some(out) = mut_output.upgrade() {
+                let mut o = out.lock().unwrap();
+                o.called_key = Some(obs_key.clone());
+                for report in batch.iter() {
+                    o.txids.push(report.tx_id.clone());
+                    o.changes.push(report.changeset.clone());
+                }
+                o.txids.sort();
+            }
+        }));
+
+        conn.register_observer(key.clone(), Arc::clone(&tx_observer));
+        assert!(conn.is_registered_as_observer(&key));
+
+        let mut tx_ids = Vec::new();
+        let mut changesets = Vec::new();
+        {
+            let mut in_progress = conn.begin_transaction(&mut sqlite).expect("expected transaction");
+            for i in 0..3 {
+                let name = format!("todo{}", i);
+                let uuid = Uuid::new_v4();
+                let mut builder = in_progress.builder().describe_tempid(&name);
+                builder.add_kw( &kw!(:todo/uuid), TypedValue::Uuid(uuid)).expect("Expected added uuid");
+                builder.add_kw(&kw!(:todo/name), TypedValue::typed_string(&name)).expect("Expected added name");
+                if i % 2 == 0 {
+                    builder.add_kw(&kw!(:todo/completion_date), TypedValue::current_instant()).expect("Expected added date");
+                }
+                let (ip, r) = builder.transact();
+                let report = r.expect("expected a report");
+                tx_ids.push(report.tx_id.clone());
+                changesets.push(report.changeset.clone());
+                in_progress = ip;
+            }
+            let mut builder = in_progress.builder().describe_tempid("Label");
+            builder.add_kw(&kw!(:label/name), TypedValue::typed_string("Label 1")).expect("Expected added name");
+            builder.add_kw(&kw!(:label/color), TypedValue::typed_string("blue")).expect("Expected added color");
+            builder.commit().expect("expect transaction to occur");
+        }
+
+        let delay = Duration::from_millis(100);
+        thread::sleep(delay);
+
+        match Arc::try_unwrap(output) {
+            Ok(out) => {
+                let o = out.into_inner().expect("Expected an Output");
+                assert_eq!(o.called_key, Some(key.clone()));
+                assert_eq!(o.txids, tx_ids);
+                assert_eq!(o.changes, changesets);
+            },
+            _ => {
+                println!("Unable to unwrap output");
+                assert!(false);
+            }
+        }
+    }
+
+    #[test]
+    fn test_observer_not_notified_on_unregistered_change() {
+        let mut sqlite = db::new_connection("").unwrap();
+        let mut conn = Conn::connect(&mut sqlite).unwrap();
+        add_schema(&mut conn, &mut sqlite);
+
+        let name_entid: Entid = conn.current_schema().get_entid(&kw!(:todo/name)).expect("entid to exist for name").into();
+        let date_entid: Entid = conn.current_schema().get_entid(&kw!(:todo/completion_date)).expect("entid to exist for completion_date").into();
+        let mut registered_attrs = BTreeSet::new();
+        registered_attrs.insert(name_entid.clone());
+        registered_attrs.insert(date_entid.clone());
+
+        let key = "Test Observing".to_string();
+
+        let output = Arc::new(Mutex::new(ObserverOutput::default()));
+
+        let mut_output = Arc::downgrade(&output);
+        let tx_observer = Arc::new(TxObserver::new(registered_attrs, move |obs_key, batch| {
+            if let Some(out) = mut_output.upgrade() {
+                let mut o = out.lock().unwrap();
+                o.called_key = Some(obs_key.clone());
+                for report in batch.iter() {
+                    o.txids.push(report.tx_id.clone());
+                    o.changes.push(report.changeset.clone());
+                }
+                o.txids.sort();
+            }
+        }));
+
+        conn.register_observer(key.clone(), Arc::clone(&tx_observer));
+        assert!(conn.is_registered_as_observer(&key));
+
+        let tx_ids = Vec::<Entid>::new();
+        let changesets = Vec::<BTreeSet<Entid>>::new();
+        {
+            let mut in_progress = conn.begin_transaction(&mut sqlite).expect("expected transaction");
+            for i in 0..3 {
+                let name = format!("label{}", i);
+                let mut builder = in_progress.builder().describe_tempid(&name);
+                builder.add_kw(&kw!(:label/name), TypedValue::typed_string(&name)).expect("Expected added name");
+                builder.add_kw(&kw!(:label/color), TypedValue::typed_string("blue")).expect("Expected added color");
+                let (ip, _) = builder.transact();
+                in_progress = ip;
+            }
+        }
+
+        let delay = Duration::from_millis(100);
+        thread::sleep(delay);
+
+        match Arc::try_unwrap(output) {
+            Ok(out) => {
+                let o = out.into_inner().expect("Expected an Output");
+                assert_eq!(o.called_key, None);
+                assert_eq!(o.txids, tx_ids);
+                assert_eq!(o.changes, changesets);
+            },
+            _ => {
+                println!("Unable to unwrap output");
+                assert!(false);
+            }
+        }
+    }
 }